Surface mount technology in the field of electronics is that in which electrical components are mounted directly to the surface of a printed circuit board or the like usually without any contacts or leads penetrating through the printed circuit board. Increased space utilization efficiency is an advantage of surface mount technology over space requirements of the prior art techniques for mounting electrical components with respect to a printed circuit board. Thus, surface mount technology provides increased density of components and/or increased capabilities for a given printed circuit board and the like; and surface mount technology also generally reduces the above board height requirements and, therefore, allows more printed circuit boards to be stacked or otherwise positioned in a given electrical apparatus.
In typical surface mount processes a surface mount electrical component is mounted directly to a printed circuit board. More specifically, the printed circuit board may have circuit traces and contact/mounting pads all printed on a surface thereof. A surface mount electrical component, such as a leaded chip carrier, an unleaded component, or the like, having plural leads, terminal pads, or the like, is placed on such contact/mounting pads. Solder may have been applied to such leads, terminal pads and/or contact/mounting pads prior to such placement. After all such components are placed on the printed circuit board, heat energy is applied to reflow the solder, such as vapor phase soldering, to complete electrical and mechanical connections between the component(s) and the contact/mounting pads and traces of the printed circuit board. Sometimes an adhesive material is used temporarily to hold the component(s) in position on the printed circuit board prior to and during such soldering.
Consistent with the surface mounting processes currently employed, electrical connectors have been mounted directly to the surface of the printed circuit board in substantially the same way as the other surface mount components are mounted, as is summarized above. In this way complete compatibility of mounting processes is achieved. An example of such an electrical connector is a device known as a header, which is a plurality of electrical contacts retained in relative position by an electrically non-conductive body. Typically such contacts are elongate pin type contacts with ends that are exposed at opposite sides, e.g., the top and bottom, of the body. The exposed contact ends remote from the body are of a shape and are so positioned to fit into electrical and mechanical engagement with the contacts of a portable connector which may be inserted over such contact ends. Such a portable connector may be a female connector having plural female contacts for engaging the male contacts of the header to provide electrical connection of respective circuits, e.g., to the conductors of a cable, another printed circuit board or the like. One or more headers may be mounted in side-by-side fashion to provide multiple rows of exposed header contacts for connection to the contacts of appropriately designed portable connectors and the like.
For consistency with surface mount processes one practice has been to bend the exposed ends of the connector e.g., header, contacts that are proximate the printed circuit board so that such contact ends can lay flat against the contact/mounting pads of the printed circuit board. Then, during the surface mounting soldering process, securement of those contact ends mechanically and electrically to the surface of the printed circuit board is accomplished in the same way that securement of the other surface mount components is accomplished.
However, such connector surface mounting process lacks certain strength and durability characteristics over prior through-the-board mounting techniques for mounting components on a printed circuit board. Specifically, whenever a portable connector is removed from the header/connector, a substantial force is applied to the connection of the contacts and pads to which they are attached; indeed, such pads themselves are not integral with the printed circuit board but are only an additional layer applied thereto. Thus, there is the possibility that the connection of the header to the printed circuit board and/or the integrity of the pads and printed circuit traces will be too easily damaged or destroyed when mechanically stressed by removing a portable connector from connection with the header connector.
Another disadvantage with the technique of using bent contacts to make connections between a connector mounted on a surface mount printed circuit board and the contact/terminal pads of the latter is the relatively large amount of space required for such contacts and the connections thereof to the printed circuit board. Such space requirement is contrary to one of the important advantages of the surface mount technique vis-a-vis other electrical components designed specifically to be space efficient in the surface mounting process. The prior techniques of coating a lead, contact, or the like with solder, e.g., using a process of dipping the lead in solder, are not satisfactory to place an adequate amount of solder on the lead to achieve reflowing of the solder into a plated through hole so as to provide a secure mechanical and electrical connection of the lead, contact, etc. to the printed circuit board.
According to the disclosures of the above earlier filed applications, an electrical component that has plural elongate leads or contacts is mountable and/or mounted in a printed circuit board compatibly with surface mount processes by placing the leads or contacts in plated through holes of the printed circuit board and effecting soldering function contemporaneously with the soldering effected during the surface mount soldering process. The leads or contacts in the holes increase the mechanical strength of attachment of the component to the printed circuit boar. The solder itself may be, for example, an adequate amount of solder paste or solder donuts applied to the contacts of the electrical component before it is placed in the printed circuit board. Retention of the solder with respect to the contacts of the electrical component may be facilitated and/or secured by a means integral with the component, such as a reservoir arrangement in the body of the electrical component. Moreover, the solder may be re-flowed to make secure mechanical and electrical connections of the electrical component contacts and respective plated through holes or other means of the printed circuit board to which attachment is intended at the same time that other surface mount components are connected by re-flowing solder, e.g. as in a vapor phase soldering or other soldering process. Methods and use of robotics or other automated equipment also are disclosed in such applications.